1. Field of the Invention
This invention relates generally to a toner supplying device included in an image forming apparatus and more particularly to a toner supplying device having two or more toner containers.
2. Discussion of the Background
In image forming devices using electrophotography, such as copying machines, facsimile devices and printers, a latent image is formed on a surface of a drum or belt-like shaped image bearing member by first uniformly charging the surface of the image bearing member and then exposing the charged surface with light which is modulated with image information. The latent image is then developed by a developing device to a visible toner image using a developer, such as, for example, a two component developer including toner and carrier. The developed toner image is transferred onto a recording medium such as a sheet of paper directly or via an intermediate transfer member, thereby forming an image on the sheet of paper.
The image forming devices of this type generally include a toner supplying device for supplying toner to the developing device as the developing device consumes the toner as it develops images. A toner container is attached to the toner supplying device. Once the toner is consumed by developing device, the image forming device generally stops the image forming operation and displays a message indicating that the toner container has run out of toner. The device returns to an operable state once the toner container is replaced with a new toner container and the toner is supplied to the developing device.
Various toner supplying devices, in which a toner container is attached, have been proposed. For example, Japanese Patent Laid-open Publication No. 2-277083 describes toner supplying device having a plurality of toner containers, which are disposed near a developing device. The toner container chosen to supply toner to the developing device is changed by rotating the toner supplying device.
Japanese Patent Laid-open Publication No. 7-219329 describes a toner supplying device, which is placed apart from a developing device to improve the maintenance operability of the toner supplying device. The toner supplying device is connected to the developing device via a toner delivery device which delivers toner by mixing the toner with air.
Further, Japanese Patent Laid-open Publications No. 4-80779 and No. 8-137227 describe a toner supplying device including a toner container accommodating device in which a plurality of toner containers can be attached. Toner discharged from each of the plurality of toner containers is merged together and conveyed to a developing device. Each of the plurality of toner containers is individually attachable to and detachable from the toner supplying device. Japanese Patent Laid-open Publication No. 8-137227 further describes that the toner container accommodating device accommodates two toner containers and when a sensor detects non-existence of toner in a toner conveying pipe to a developing device, an agitator of one of the two toner containers which has not been operated, begins to rotate to supply toner therefrom.
Furthermore, the present inventors have proposed a toner supplying device which includes a plurality of toner containers and which is disposed in a position apart from a developing device. Toner is conveyed to the developing device from the toner supplying device via a toner conveying device connecting the developing device and the toner supplying device.
The toner supplying devices including a plurality of toner containers, which are described in the prior art, have a problem that the operability of attaching and detaching a toner container to and from the toner supplying device is poor. Further, even if the toner supplying device is configured such that another toner container starts to discharge toner immediately before or when the operating toner container becomes empty, selecting an optional toner container among from a plurality of toner containers, which are attached to the toner supplying device, before the operating toner container becomes almost empty or completely empty, is not possible. If a toner container, which is operated to discharge toner following the operating toner container, is empty, an intermittent supply of toner to a developing device occurs and a decrease in the volume or density of the toner is caused in the developing device. Consequently, the resulting image quality is deteriorated. Stoppage of the image forming operation may also occur. Further, if a toner container is kept unoperated for a long time after having been attached to the toner supplying device, the toner in the container deteriorates, and the resulting image quality may be deteriorated.
The image forming devices as described above typically further include a cleaning device that removes residual toner remaining on the photoconductor or the intermediate transfer member to prevent contamination of subsequent images which will be formed thereupon. The image forming devices also include a cleaning device that removes toner remaining on the transfer belt and a conveying belt which conveys a transfer sheet to the fixing unit. Residual toner collected by the cleaning devices is generally put into a discardable toner container, i.e., a toner container for storing discardable toner, and is disposed of by a service person or a user of the apparatus.
Recently, demands for recycling residual used toner, which is collected by cleaning devices of an image forming apparatus, have increased, and mechanisms for conveying collected used toner to a developing device of the apparatus or to a toner supplying device that supplies toner to the developing device have been proposed.
Residual used toner collected by cleaning devices generally includes paper dust, which is produced from a transfer sheet. Paper dust is produced, for example, when the transfer sheet passes between the transfer device and the photoconductor or the intermediate transfer member. The residual used toner also includes coagulated toner particles which are larger than unused toner particles. If the residual used toner is recycled for image formation, paper dust and/or coagulated toner particles included therein may form abnormal toner images. For example, white spots may be formed in a part of a toner image formed by toner which includes paper dust. A part of a toner image formed by toner which includes a large coagulated toner particle may be blurred.
To solve such problems, Japanese Patent Laid-open Publication No. 7-77906 proposes to provide a filter for removing paper dust and coagulated toner particles from the collected used toner so that only reusable used toner separated from non-reusable used toner is recycled to the toner supplying device.
Further, as related art, Japanese Patent Laid-open Publication No. 5-293443 describes a technology to remove large toner particles with a screen at the last stage of a process of manufacturing toner for image forming devices.
Image forming devices including such a toner supplying device having a plurality of toner containers and a mechanism for recycling residual used toner collected by cleaning devices to a developing device or to a toner supplying device as described above have a problem that a toner container containing new toner, a container containing reusable used toner and a container containing non-reusable used toner are separately located in the apparatus and thereby scattering of toner and consequent soiling with scattered toner occurs in various parts of the image forming devices. In addition, the operability of attaching and detaching respective toner containers is poor.